Somis, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

730
FXUS66 KLOX 121138
AFDLOX

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
438 AM PDT Sat Apr 12 2025

.SYNOPSIS...12/436 AM.

Strengthening onshore flow will bring a cooling trend into early
next week. Night through morning low clouds will become a staple
of the forecast over the weekend, pushing into the coastal slopes
of the mountains by mid week. A cooler weather pattern is expected
through much of next week as a series of low pressure systems move
over the region. Night through morning drizzle or afternoon and
evening mountain showers cannot be ruled out for periods next
week.

&&

.SHORT TERM (TDY-MON)...12/432 AM.

The latest water vapor imagery shows southwest flow aloft firmly
in place as broad upper-level troughing moves into the region. A
much more entrenched marine layer cloud deck is developing early
this morning with low clouds and fog expanding rapidly across the
coast and valley areas. There is a chance that clouds could be
stubborn to clear today. The latest high-resolution model
solutions lean toward that idea, but the forecast does not buy
into the idea totally. Model forecast guidance indicates a
broader temperature-dewpoint temperature spreads than ideal for
keeping clouds lingering. That being said with trough aloft
approaching and the time of year, it would not be surprising to
see clouds lingering longer. The current NAM-WRF solutions
suggest KLAX-KDAG surface pressure gradients hovering near 7.5 mb
onshore this afternoon. With current gradient already running
almost 4 mb more strongly onshore than yesterday and more than a
millibar more strongly onshore than progged, this wrinkle in the
forecast will need to be watched closely.

Night through morning low clouds and fog will become a staple of
the forecast as moderate to strong onshore flow is likely to
develop across the region. While gradients will weaken slightly
over the coming days, onshore flow and a well established marine
intrusion will continue. A cooling trend is very likely to persist
through the weekend.

A shortwave trough moving south of Aleutian Islands this morning
will drop down into the region late in the weekend, cutting off
from the flow off the California coast between Sunday and Monday.
This trough will reinforce onshore flow and likely deepen the
marine layer depth. The trough will likely stall out off the coast
for several days and keep a cooler weather pattern in place.

.LONG TERM (TUE-FRI)...12/437 AM.

A series of cutoff troughs of low pressure are expected to move
over the region for next week. There is quite a bit of
uncertainty with the finer details of the forecast. Confidence
remains high in a cooler weather pattern lingering as cluster
analysis suggests a broader troughing pattern lingering through
much of the week. The uncertainty comes from the exact movement of
upper-level low pressure systems. Night through morning drizzle
or mountain showers and thunderstorms cannot be ruled out entirely
given the pattern. The latest forecast ensembles have a few
members generating precipitation for the first trough moving over
the region between Tuesday and Wednesday, but this is likely
underdone due to the convective nature of the air mass. In the
latest deterministic solutions, there are periods of time where a
difluent flow pattern develops ahead of a 500 mb cold pocket
approaching -22 degrees Celsius. The current forecast emphasizes a
deeper marine layer with a cooler weather pattern lingering, but
this will be need to monitored closely.

As we get out into late next week, a stronger cutoff low will
likely move over the region. This could be the system that
could bring a higher chance of precipitation. More than of the
forecast ensembles have QPF with the system for late next week.
There is a also a chance that this system could bring snow levels
down to the 4000 foot level, as well. About a fifth of the EPS
members generate snow for KSDB. As stronger onshore flow will
likely develop with the trough, gusty southwest winds are possible
for the interior portion of the area. EPS wind gusts means
approach wind advisory criteria for several days late next week
for KPMD and KWJF. While the forecast goes with NBM values for the
current time due to the uncertainty, future shifts may need to
take a closer look at the finer details as we get closer into the
time period.

&&

.AVIATION...12/0002Z.

At 2228Z at KLAX, the marine layer was around 400 feet deep. The
top of the inversion was near 1700 ft with a temp of 23 C.

Overall, moderate confidence in 00Z TAF Package. High confidence
in VFR conds for desert airfields (KPMD, KWJF) thru fcst pd. There
is a 15% chance of VLIFR to LIFR conds at KBUR and KVNY from 10Z
to 16Z Sat. There is a 30% chance of LIFR conds at KSMX from 08Z
to 15Z Sat.

There is a 30% chance of LIFR/IFR cig arrival at KSBA from
12Z to 18Z Sat. There is a 30% chance of LIFR conds at KOXR from
10Z to 17Z Sat - lower chances (10-20%) at KCMA. 30% chance of
LIFR conds at KSMO and slightly higher at KLGB.

Timing of cig/vsby restrictions may be off +/- 3 hours. Flight
cats may be off one or two.

KLAX...Moderate to low confidence in 00Z TAF. Arrival and
departure of cigs may be off by a couple of hours. There is a 30%
chance of LIFR conds (<3SM,